Effects of LSD-25 on the EEG and Photic Evoked Responses

Lysergic acid diethylamide (LSD-25) reduces the amplitude of electroencephalographic (EEG) signals, causes alpha rhythms to disappear, and produces low-voltage fast or desynchronized tracings. Alpha frequencies increase by 0.5 to 4 cycles per second, with one report noting a rise from 11.6 cycles per second. These findings are based on surface and depth recordings in humans. The literature on LSD's behavioral and pathophysiological effects contains over 1,000 publications since its psychosomimetic properties were discovered in 1947.

Study at a glance

Abstract

SINCE the accidental discovery of the Psychosomimetic properties of Lysergic acid diethylamide (LSD-25) by Stoll,1in 1947, a great amount of work has been carried out to elucidate the behavioral effects and pathophysiological mechanisms of action of this substance. The literature on this topic is steadily growing and contains now more than 1,000 publications.2 There are several studies available that report on the electroencephalographic changes resulting from LSD administration to humans as seen by surface recordings3-9and there are also some observations on changes in the human depth electrogram.10-13It is generally agreed that the amplitude of the EEG decreases, α-rhythms tend to disappear and the tracings become of the lowvoltage fast or desynchronized type. Gastaut4reported that the average α-frequencies are increased by 0.5 to 4 cycles per second (cps) and Grey Walter7noted an increase from 11.6 to